A metal oxide semiconductor field effect transistor (MOSFET) commonly includes an active area which contributes to the conduction of the transistor device and an edge termination region around the perimeter of the transistor, surrounding the active area. The edge termination area typically includes an edge termination structure which is designed to have the same or higher breakdown capability as the active area transistor.
US patent application US 2009/0090967 A1 discloses a MOSFET device with active area and edge termination area charge balance to provide uniform voltage breakdown across the active and termination area, whilst obtaining a suitably low drain source on resistance (RDSon).
However, further improvements to transistor device structures and edge termination structures are desirable in order to produce more reliable transistor devices with good performance.